from google.appengine.ext import ndb
class User(ndb.Model):
    _use_cache = False
    _use_memcache = False
    city = ndb.StringProperty()
    love = ndb.StringProperty()
matsuo_sensei = User(id="matsuo", city="Montain View", love="compute").put()
kaz = User(id="kaz", city="Tokyo", love="python", parent=matsuo_sensei); kaz.put()
User(id="proppy", city="Tokyo", love="golang", parent=matsuo_sensei).put()
kaz.love = "golang"; kaz.put() # max: 1 write/s
print User.query(User.city == "Tokyo", ancestor=matsuo_sensei).fetch() # kaz:golang,proppy:golang
print User.query(User.city == "Tokyo", ancestor=matsuo_sensei).fetch() # kaz:golang,proppy:golang
print User.query(User.city == "Tokyo", ancestor=matsuo_sensei).fetch() # kaz:golang,proppy:golang
